The present invention relates to a process for inhibiting the corrosion of equipment made of titanium or of alloys containing titanium by aqueous solutions containing a peroxy compound and more particularly, by alkaline aqueous solutions containing a peroxy compound such as hydrogen peroxide.
Titanium and its alloys are materials frequently used in the manufacture of equipment for industrial installations for bleaching of cellulose materials. These installations often include multi-purpose apparatus in which various kinds of widely differing reagents can be used. This is the case for example, in textile bleaching installations, in dynamic paper pulp bleaching installations, and in certain conventional kraft pulp bleaching installations, which include an all-purpose final stage. Equipment in such installations is made at least in part of titanium or one of its alloys.
Since titanium and its alloys can be corroded by certain aqueous solutions commonly used in bleaching, such as alkaline aqueous solutions of peroxy compounds, the choice of reagents or the concentration at which they should be used in installations having surfaces which are in contact with such solutions, and which are made of titanium or one of its alloys, is limited.
To inhibit the corrosion of titanium under these conditions, the suggestion has been made (T. M. Sigalovskaya, et al. Zashchita Metallov, 1976 Vol. 12 (4), P363-367) that sodium hexametaphosphate or sodium silicate be added to the corrosive solution. However, the reduction in corrosion observed is insufficient for the process to be applied industrially.